1. Field of the Invention
Embodiments of the present invention generally relate to a process for making polyethylene blow molding resin. More particularly, embodiments of the present invention relate to a slurry polymerization process for making polyethylene blow molding resin using a titanated chrome catalyst.
2. Description of the Related Art
Chrome catalysts, sometimes termed Phillips catalysts, are known catalysts for olefin polymerization. In these catalysts, a chromium compound, such as chromium oxide, is supported on a support of one or more inorganic oxides such as silica, alumina, zirconia or thoria. In olefin polymerization, chrome catalysts have been titanated to provide increased catalyst activity and reduced induction time for polymerization. Titanated chrome catalysts are known to produce polyethylene resins having broader molecular weight and increased melt index and ESCR.
U.S. Pat. No. 3,976,632 and U.S. Pat. No. 3,996,163 disclose synthesizing chrome catalysts in slurry, and adding a titanium ester to titanate the chrome catalyst. The mixture is dried to a free-flowing power, which is then activated in hot air.
EP 0 314 385 discloses another method for synthesizing titanated chromium on silica catalysts useful for gas phase polymerization of ethylene. The catalyst is introduced with an organomagnesium compound, RMgR′, either prior to feeding or within the polymerization vessel. The catalyst is titanated using a number of titanium halides, alkyl titanium halides, alkyl titanium alkoxides, alkoxy titanium halides or titanium alkoxides.
EP 0 882 740 discloses the titanation of chromium based catalysts using alkyl titanium alkoxides or titanium alkoxides, which are added to the chromium containing catalysts while at a temperature of at least 300° C. in a fluidized bed under nitrogen.
U.S. Pat. No. 3,780,011 discloses the modification of chromium on SiO2 catalyst by the addition of a titanium ester to a bed of fluidized catalyst held at a temperature of at least 300° C. The esters have the general formula RnTi(OR1)m, wherein n+m=4.
U.S. Pat. No. 4,016,343 discloses titanation of silica prior to the addition of the chromium compound to the titanated support. The chromium compound is a tetravalent alkoxide and the titanated support is prepared using titanium esters of the general formula RnTi(OR1)m, wherein n+m=4, TiX4, TiO2, alkanolaminetitanates, and titanium acetylacetonate compounds. Titanation is accomplished by mixing the support and the titanium compound and heating at a temperature of about 150-1200° C.
U.S. Pat. No. 4,184,979 discloses the preparation of catalyst by dry blending chromium(acac)3 with a silica support. The mixture is then heated to a temperature of 230-540° C. The catalyst is titanated by adding the liquid titanium compound to a fluidized bed of the chromium catalyst or by passing vapors of the titanium compound through the fluidized bed of the chromium catalyst.
U.S. Pat. No. 4,368,303 discloses a catalyst produced by forming a silica hydrogel; drying said hydrogel to form a xerogel; anhydrously incorporating a titanium compound into said xerogel; wherein chromium is introduced by either coprecipitating same with said silica hydrogel, by combining a water-soluble chromium compound with said hydrogel, or adding anhydrous solution with said hydrogel, or adding anhydrous solution of a chromium compound soluble in non-aqueous solvents to said xerogel; and after said drying and after said chromium is introduced, activating the resulting dried, chromium-containing composition by means of an activation procedure which comprises treatment at an elevated temperature in an atmosphere containing oxygen. In this manner, the process incorporates Ti into the silica rather than deposits Ti on the surface.
U.S. Pat. No. 4,384,987 discloses a method for preparing a polymerization catalyst comprising the steps of contacting a material comprising silica-supported chromium oxide or a compound oxidizable to chromium oxide with a solution of a permanganate compound; heating the thus-contacted material in a reducing atmosphere at a temperature in the range of about 600° C. to about 1100° C.; and then heating the material in an oxygen-containing atmosphere at a temperature in the range of about 450° C. to about 1000° C. for at least about one-half hour.
U.S. Pat. No. 4,402,864 discloses the use of titanium polymers for titanation. The polymers are prepared from Ti(OR)4 and water. The soluble titanium polymer, e.g., TiO2()—iC3H7)6 is most conveniently added to a hydrocarbon slurry of the support.
U.S. Pat. No. 4,728,703 discloses the preparation of a chromium on silica catalyst by combining a slurry of silica in an alkane with finely divided CrO3, then adding alcohol, then adding Ti(OR)4. The mixture is dried, and then heated as a fluidized bed first in nitrogen and then in air.
U.S. Pat. No. 5,573,993 discloses a process for preparing activated catalyst for the polymerization of olefins in the absence of solvent. A mixture of a powdered chromium salt with a support is heated to a temperature below the melting temperature of the chromium salt for a period of between 0.5 hours and 18 hours, and then the mixture is heated to an activation temperature.
Other references include EP 0279890; EP 1 172 381; WO 01 32307; DE 2622755; U.S. Pat. No. 3,887,494; U.S. Pat. No. 4,877,763; U.S. Pat. No. 5,096,868; U.S. Pat. No. 6,174,981; U.S. Pat. No. 6,921,798; US 2003/0232715; US 2004/0192863; and US 2006/0089468.